Safety valve for electrical submersible centrifugal pumping system

ABSTRACT

Various implementations include a safety valve for mounting in a landing nipple in a wellbore. The safety valve includes a composite housing having a central passage, a shutoff element and a control mechanism. The shutoff element includes a collet and a movable mandrel having stops located in the upper part. When the shutoff element moves axially, the stops extend through the composite housing to interact with a landing nipple stop surface. The control mechanism includes a spring-loaded tubular plunger having a ring piston on its upper outer surface and longitudinal openings in its lower part, the openings being configured to align with openings in the composite housing. The movable mandrel is connected to the safety valve head at the mandrel top and rests against the plunger at the mandrel bottom. The movable mandrel has grooves and shoulders on its outer surface, which allow for taking one of the fixed positions.

FIELD OF THE INVENTION

The invention relates to the oil industry and can be used for oil production.

BACKGROUND OF THE INVENTION

A safety valve is known in the art [U.S. Pat. No. 7,967,074, published on Jan. 28, 2011], the safety valve comprising a housing with a central longitudinal passage, a shutoff element with retractable dies in the upper part of the housing, a connecting element, channels for fluid flow, valve elements, and a sleeve moving as affected by springs and a landing nipple. Such safety valve is mounted inside a failed tubing mounted subsurface safety valve, makes it permanently fully open and uses its hydraulic control line. The disadvantage of the valve is that it cannot be used independently, without the failed main (tubing mounted) valve, the hydraulic line of which it uses.

The closest prior art solution for the claimed device is a safety valve for an electrical submersible centrifugal pumping system [RU 2516708, IPC E21B34/06, published on May 20, 2014]. The valve is controlled by differential pressure on both sides and is located in the landing nipple. It comprises a composite housing with a central passage, a packer, a shutoff element comprising a movable mandrel and a collet having blades and a head, a control mechanism for the shutoff element, a rod with openings and a circular groove. The rod has a check valve cage in the upper part, a ring piston in the middle part and a control mechanism comprising a stepped ring piston at the bottom end, the control mechanism being pressed with a nut and equipped with a cup with a collar forming a movable connection with an extension connected to the composite housing provided with a separating washer and a lower adapter in the connection area. The stepped ring piston has a sleeve forming a movable connection in the boring of the lower adapter and a ring chamber with an extension, the chamber hydraulically connected with the axial channel of the sleeve by means of a drain opening. The cavities above the ring piston and above the collar are hydraulically connected to the cavity under the packer by means of openings. The cavity of the ring chamber above the separating washer is connected to the axial channel of the rod by means of an opening. Further, the shaped nut is connected to the housing of the bypass valve having a landing surface at the end part facing the landing seat of the lower adapter, in the axial channel of which a seat with a spring-loaded ball valve is mounted. The collet is installed inside the composite housing. The prior art safety valve is used to shut off the wellbore during workover procedures without killing the well.

The disadvantages of the prior art safety valve include the design complexity due to the presence of two ball valves and three springs, which reduces the valve reliability, and the constraints related to using the valve in slim wells.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a reliable automatic safety valve for shutting off the inlet channel of the electrical centrifugal pump from well fluid coming from the annulus when the electric motor is disabled, and ensure uninterrupted supply of well fluid when the electric motor is enabled, with the possibility of using such safety valve in slim wells.

The technical effect is achieved by the design of a safety valve for electrical submersible pumping systems. The valve is installed in a landing nipple and comprises a composite housing having a central passage, a shutoff element consisting of a movable mandrel, a collet, and a control mechanism including a spring and a valve. According to the invention, the shutoff element comprises stops located in the upper part of the movable mandrel and extendable through composite housing through grooves under the axial movement of the shutoff element, thus interacting with a stop surface of the landing nipple. The control mechanism comprises a spring-loaded tubular plunger having a ring piston on its upper outer surface and a series of longitudinal openings in its lower part configured to align with similar openings in the composite housing to allow the safety valve functioning. The movable mandrel is connected to the head of the safety valve on the top and rests against the plunger from the bottom.

In order to provide a fixed position inside the composite housing when mounting the safety valve in the landing nipple, the movable mandrel comprises a series of grooves and shoulders on its outer surface.

Besides, the stops are pressed by leaf springs when the valve is run in the well.

The composite housing also comprises a seal housing with a through opening for fluid inlet and an outer elongated groove accommodating the sealing unit.

The technical effect is achieved by the fact that, when the electrical submersible pump is running, reduced pressure compared to that of the annulus is created in the inner cavity of the safety valve, and the plunger is displaced due to the resulting differential pressure. In this case, the longitudinal through openings at the bottom of the plunger align with similar openings in the composite housing, thus ensuring passage of the well fluid through them to the inlet of the electrical submersible pump. When the pump is off, the pressure in the annulus and in the inner cavity of the safety valve is equalized, the spring is released and makes the plunger to displace towards the movable mandrel; as a result, the longitudinal through openings in the plunger and the housing fail to align, and the flow of well fluid into the pump stops.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by the drawings, where

FIG. 1 shows the safety valve in the longitudinal section;

FIG. 2 shows the safety valve being lowered into the well in the longitudinal section;

FIG. 3 shows a schematic of the safety valve mounting inside the landing nipple;

FIG. 4 shows a diagram of isolated volumes of fluid when the motor is disabled; and

FIG. 5 shows a scheme of fluid movement when the electric motor is running.

DETAILED DESCRIPTION OF THE INVENTION

The safety valve (FIG. 1) comprises head 1, lock housing 2, leaf spring 3 pressing stops 4, shifting tool with spring 5 and pins 6 arranged in groove 37 on the outer side of lock housing 2, lock balls 7, movable mandrel 8, release housing 9, collet 10, stop housing 11, seal housing 12 with sealing unit 13, adapter housing 14, valve housing 16, plunger 15, spring housing 17, spring for moving the plunger 18, guide rod 19, base 20, collar 21, through openings 22 in the plunger 15, external groove 23 in the movable mandrel 8, shoulder 24 on the release housing 9, inlet opening 25, sleeves 26, longitudinal through opening 27 in the valve housing 16, sleeves 28, ring piston 30, and stop surface 36 of the lock housing 2.

Head 1 has stop surface 31 resting against stops 4 at the end of the outer diameter from the side of movable mandrel 8. Head 1 has a threaded connection with movable mandrel 8 and is sealed by means of a sealing sleeve located in the end groove on the inner surface of head 1. Through central passage 32 extends along the safety valve starting from head 1. On the outer surface of movable mandrel 8, there are groove 33 (FIG. 3), groove 23 and shoulder 34 (FIG. 1) designed to secure the mandrel in one of the positions using collet 10 and lock balls 7.

Inside the central passage 32 of the composite housing, between movable mandrel 8 and spring 18, there is hollow tubular plunger 15 configured for axial movement. The movement of plunger 15 is limited by spring 18 on the one side and by resting against the lower side of movable mandrel 8 on the other side. Plunger spring 18 is mounted on guide rod 19 connected to base 20 with a thread. In the upper part, on the outer surface of plunger 15, ring piston 30 is arranged with a groove for sealing sleeve 21 resting against valve housing 16. In the lower part of plunger 15, a series of longitudinal through openings 22 is formed.

Movable mandrel 8 with collet 10 secured from below and having in its upper part stops 4 extendable through the rectangular grooves of lock housing 2 forms the shutoff element of the safety valve.

When running in the well, stops 4 are held by leaf springs 3, and after the procedure is completed, springs 3 interact with the stop surface of the landing nipple and are extended. Lock housing 2 rests against the shifting tool pins 6 from below through the shifting tool springs 5. On the inner surface of the shifting tool pins 6, there is bore 35 (FIG. 2) for the lock ball 7, and stop surface 29 on the outer end of the shifting tool pins 6. From below, the shifting tool pins 6 rest against release housing 9 which has shoulder 24 (FIG. 1) on the lower surface to secure collet 10. Then release housing 9 has a threaded connection with stop housing 11, which, in turn, has a threaded connection with seal housing 12 having through opening 25 for fluid inlet. On the outer surface of seal housing 12, an elongated groove is formed for sealing unit 13, and on its inner surface a bore with sleeve 26 is formed. Seal housing 12 has a threaded connection with adapter housing 14 with valve housing 16 screwed onto its lower end. The valve housing has longitudinal through opening 27 the shape of which is similar to the shape of longitudinal through openings 22 in plunger 15. On the lower surface of valve housing 16 bores for sealing sleeves 28 are formed. Valve housing 16 has a threaded connection with spring housing 17 connected to base 20.

The device operates as follows.

When running the unit in the well (FIG. 2), the safety valve is mounted below the electrical submersible pump (not shown). Movable mount 8 is blocked by release housing 9 using lock balls 7 with stops 4 hidden in lock housing 2 and held there by leaf springs 3. At this time, shifting tool pins 6 are located to the right of stop surface 36, and therefore, as soon as the safety valve falls onto the stop surface of the packer nipple, the shifting tool pins 6 are fully engaged, thus ensuring timely mounting of the valve.

When the safety valve reaches the setting depth, and the shifting tool pins 6 touch the surface on the packer landing nipple with stop surface 29, the four shifting tool pins 6 are simultaneously displaced, and lock balls 7 extend from bore 33 of movable mandrel 8. Then, under the weight of the tubing string, movable head 1 connected to mandrel 8 moves downward, while the head stop surface 31 pushes stops 4 out, and movable mandrel 8 is fixed in collet 10 by means of groove 23. The safety valve is fixed at the set depth with its stop surface 36 resting against the stop surface of the nipple (FIG. 3). Sealing unit 13 isolates well fluid present below the sealing unit (FIG. 4).

After the safety valve is installed, three isolated volumes are formed: the inner area, the outer area and the area below the sealing unit (FIG. 3). The pressures of the outer area and the inner area are designated as P1 and P2, respectively.

If the pump is not running and P1=P2, then plunger 15 is located at the top under the action of compression force of plunger spring 18 (the safety valve is closed), and the oil, gas and water mixture from the area below the sealing unit cannot enter the inner cavity of the safety valve (FIG. 4).

If the pump is running, then P1>P2 and, due to the differential pressure, well fluid from the outer area, moving towards a lower pressure area, enters through opening 25 into the cavity formed by the inner surface of seal housing 12, the outer surface of plunger 15, the surfaces of sleeve 26 and ring piston plunger 30 (FIG. 1), and causes plunger 15 to move downward (FIG. 5). Longitudinal through openings 22 align with similar openings 27 in valve housing 16. The valve switches to the open position in which the oil, gas and water mixture from the area below the packer can enter the inner area of the safety valve, and then flow into the pump, thus ensuring its continuous supply.

When removing the safety valve, an upward pull with a force equivalent to the weight of the tubing string is required.

Thus, the use of the safety valve increases operational reliability of the electrical submersible pump by ensuring uninterrupted supply of well fluid when the electric motor is running and allowing to shut off the supply of well fluid automatically when the pump is not running.

The design of the claimed safety valve allows it to be used in wells of any diameters, including slim wells. For this it is necessary to reduce the size of the safety valve in proportion to the well diameter. 

1. A safety valve for electrical submersible pumping system, the pump being mountable in a landing nipple and comprising a composite housing having a central passage, a shutoff element including the movable mandrel and the collet, and a control mechanism comprising a spring and a valve, the safety valve characterized in that the shutoff element comprises stops located in the upper part of the movable mandrel, said stops being arranged, when the shutoff element moves axially, to extend through the composite housing through grooves and thus interact with a stop surface of the landing nipple, the control mechanism comprises a spring-loaded tubular plunger having a ring piston on its upper outer surface and longitudinal openings in its lower part, the openings being configured to align with similar openings in the composite housing to allow functioning of the safety valve, and the movable mandrel is connected to the head of the safety valve at the mandrel top and rests against the plunger at the mandrel bottom.
 2. The safety valve according to claim 1, characterized in that grooves and shoulders are made on the outer surface of the movable mandrel to fix its position inside the composite housing when mounting the safety valve in the landing nipple.
 3. The safety valve according to claim 1, characterized in that the stops are pressed by leaf springs.
 4. The safety valve according to claim 1, characterized in that the composite housing comprises a seal housing having a through opening for fluid inlet and an outer elongated groove accommodating a sealing unit. 